A Brief History of Time
by Elsanna Potato Corner
Summary: Scientist sisters Elsa and Anna accidentally created quantum gel that can take them to a different time/space continuum every time it exploded. [Elsanna, mAU, incest]


**A Brief History of Time**

 **Prompt:** There was an explosion.

* * *

Elsa coughed, waving a hand, trying to clear the smoke from around her. "Dammit, I didn't think that would have happened. I was hoping for something… a little less explosive, maybe?"

Anna let out a loud laugh as she rubbed at the smear of soot covering her face, barely affected by the smoke."That was awesome!" She whooped loudly and threw her arms in the air. "Let's do that again!"

"No Anna, let's not do that again. Something went horribly wrong and I have to figure out how to fix it…" she trailed off mumbling to herself. Her formula still wasn't quite right obviously, and who knew how long it would take to fix it.

Elsa's sentence skidded to a halt as she took a careful look at their surroundings. No longer were they in their laboratory. No laboratory could be this refined looking with high pillars and frivolous decorations and… is that a freaking THRONE?

Indeed, it was. A throne made of swords, to be exact. It towered at least two or three meters tall–a chaotic mess of blades that looked less and less like a throne the more she stared at it. She had no doubt that whoever sat on it would have to be _extremely_ careful, lest they accidentally cut themselves on the multitude of swords. Before she could say anything else, however, the sound of a door opening reached her ears.

Anna widened her eyes and grabbed Elsa's hand, trying to hide.

"What the hell are you doing?" Elsa whispered. Anna just shushed her, putting a hand over her mouth.

Anna dragged them behind the throne, careful to not touch anything or make any sudden movements.

Elsa gave Anna a confused glance, the girl's hand still clamped firmly over her mouth, before she turned to see who had entered the room.

A young, lone, blonde headed boy swaggered in the throne room, swinging a crossbow by his side. As he strode toward the iron throne, Anna had the unfortunate urge to sneeze, and before Elsa had a chance to cover her nose, Anna's sneeze/yell echoed through huge chamber.

Startled, the boy swung up the crossbow into its firing position and aimed it toward the still hiding girls. "Come out now and your king might spare you. I will give you until the count of three… One… Two… Thr-" And in the midst of three, the crossbow misfired, shooting a bolt towards the iron throne and ricocheting it back at the boy. It struck his heart and he fell dead on the floor. Another explosion rocked the room.

* * *

"I think I've used up my lifetime quota of explosions today." Ears still ringing, Elsa stood up from their sprawling position on the floor, brushing her clothes then dragging Anna with her towards the throne room's doors. She's still not exactly sure where they are but judging the outfits of the dead blond man, it seemed they've been sucked into the medieval past. Oh the things you can do with quantum gel! She's going to be rich when they return to their timeline, she can buy Anna anything she wants and-

"Your Majesty?"

Elsa swirled around fast enough to nearly break her own neck, and saw an equally startled old maid looking at her.

There was a sudden pounding in her head, and her vision seemed to blur a little. Beside her, Anna groaned, holding a hand to her forehead.

 _Are we…Are we shifting again?_

Elsa looked up, eyes squinting…and those eyes promptly widened at the sight of her old nanny standing there.

"Your Majesty, are you alright?" Gerda asked, her brow furrowing in concern, "And you, Princess?"

"Wh-What? Where are we?" Elsa groaned, hands rubbing her temples. "And why is my head killing me?"

"Elsa… look," Anna's eyes were wide. She was looking at a painting of the two of them, side by side. The blonde one, Elsa, was standing poised with a blank expression on her face. Anna was sitting in a chair, hands neatly folded into her lap.

"This makes no sense," Elsa stood up, fear and confusion in her eyes.

Elsa's face suddenly paled as she noticed something. "Anna…." She breathed, "Our hands."

Fit snugly on both women's ring fingers sat a ring. Identical from the pale blue color to the stone that looked exactly like a snowflake carved from ice. It was clear that those rings weren't just standard bands but rather….

"Are those wedding rings?"

"Your Majesty, did you forget about your engagement?" Gerda tittered. "And what odd clothes you're wearing! What kind of white dresses are those? Actually, never mind that, you both must get ready for your engagement ball! All of the important kingdoms will be there, so you both must look magnificent! Oh, and be wary of the Southern Isles people, they will be there as well."

* * *

"What kind of advanced past society is this if they allow two women to marry?" Elsa whispered as they followed Gerda to the changing room. The woman apparently did share the same name as their nanny, not just her appearance. Both Elsa and Anna were smart enough to keep their mouth shut and played along until they could figure out how to get out of this situation. Who knew what kind of fate awaited them if all these strangers found out they're imitating the monarchs.

" _That_ 's the first thing you decide to ponder on? How about freaking out a bit at the fact that you and me are being forced to engage in a few hours?" Anna whispered back..

Elsa shrugged, "It's only pretense. It's not like we have to do anything even if we can't figure out how to get back before they force us to marry."

 _Liar_. Elsa couldn't help but became acutely aware of the guilty happiness she's feeling at the prospect of a _fake_ engagement with her little sister, but decided to play it cool.

"Here you are," Gerda said as she opened the door to the changing room, giving them both a knowing smile as they filed in, "Do try not to take _too_ much time. We wouldn't want to cause a scandal this early now, would we?"

And with that, the maid closed the door, leaving them both alone once more.

…But not for long.

Before either of them could even _begin_ to discuss a plan, the closet door suddenly burst open, revealing…

"W-Wait a second…Elsa?!" Anna looked back and forth between her sister and her frantic-looking doppelganger, who was garbed in a tattered lab coat marred with burns and dirt. "There are two of you?!"

"I-I-I…" Elsa stuttered over her words, staring at the look alike. "I… you look like me? Except… not as burned. How the hell did I get here?"

"I don't know! You tell us," Anna widened her eyes, looking between the two blondes. "Wait, did you do what we did? Did you… time travel?"

The Elsa, from the closet, shrugged, "I think so…" she trailed off, staring at the other blonde.

Elsa began to get uncomfortable under the intense gaze of her clone and stood up, beginning to pace restlessly. The other Elsa stood, brushing at her burnt coat and fixing her mussed hair as best as she could…which wasn't very well but at least she no longer looked she recently came out of an explosion.

"So this is weird." Anna finally voiced. "One minute me and Elsa are doing an experiment and the next we're time travelling, getting married and discovering a time paradox with another Elsa. What else is going to happen?"

While Anna was freaking out with the possibilities, Elsa couldn't help but noticed the other Elsa's eyes were glued on her baby sister in a less than sisterly way. Elsa instinctively growled and stepped in front of her sister, hindering the other girl's gaze. It seemed to be effective since the other Elsa snapped out of her trance and turned her gaze away from both of them. _What was that all about? She certainly can't be me. I would never-_

Her train of thought came to an abrupt end when another explosion resounded.

* * *

"That's it! I've had enough!" Anna stripped off her lab coat and her goggles, tossing them on the floor.

"Anna..." Elsa tried to speak. They were both so shaken, and neither of them knew what to do.

"I mean, the time travelling thing was cool at first, but we need to get _home._ "

"But how?"

"I don't know, I just-"

"Alright, calm seems that every time we explode, we are 'teleported' somewhere… and it hasn't lasted long yet. But first, where are we now?"

The two of them looked behind, and… smoke filled their vision, three hundred and sixty degrees. In the bit they could see were rows and rows of neatly arranged tombstones.

Elsa frowned, kneeling down by the nearest grave, waving the billowing fog from her face. The stone itself was mottled and streaked with soot, but she could somewhat make out the inscription carved into the marble.

"The last enemy that shall be destroyed is death," she read aloud, her brows furrowing at the strangeness of the message. "How odd. What do you think, Anna?" She looked up from her examination to find that her sister was no longer by her side. "Anna?"

 _Shit, this isn't good,_ Elsa thought as she glanced around, eyes frantically searching for any sign of her sister. _We could make another jump at any time!_

"Anna!" she called, panic seeping into her voice. A raven cawed somewhere nearby, and Elsa hugged her arms around herself as goosebumps rippled across her skin.

 _Oh shit, where is she?_ Elsa thought, panicking. "A-Anna?" She called out, looking around. "Fog, there has to be so much fog, doesn't there?" Elsa muttered, looking around. "Anna, answer me… please."

Elsa tensed up, hearing the sound of footsteps coming closer to her. They weren't the kind when someone was trying to be quiet, it was the heavy kind. The kind where someone wants to be noticed.

Elsa slowly turned around, visibly paler, "A-Anna?"

"Elsa!" Anna called out as she ran, feeling a chill as all she could see was graves and fog no matter which direction she looked. It was creeping her out, and losing Elsa was the rotten cherry on top of an incredibly lousy cake.

"Elsa!" She cried out again. Frustration was mounting, as was the fear. However, upon seeing a shadowy figure just up ahead, a beaming smile lit up Anna's freckled face. "Elsa! There you are! I've been looking for you! Hey isn't this place just the creepiest? When are we going to leave?"

As the shadowed figure turned around, Anna realized that it wasn't her sister. Far from it, actually. A skeletal vision of her ex-boyfriend Hans swayed before her, his body strung up on a tree. "Here hangs a traitor," read the wooden sign next to him. As the realization sunk in, Anna screamed.

A pair of arms grabbed her from behind. Anna's scream got impossibly louder at once. She tried to elbow her attacker in a frantic attempt to break free.

"ANNA! CALM DOWN, BABY! It's me!"

Recognizing the familiar voice of her older sister, Anna relaxed and ceased her struggle. The arms around her also loosen enough for her to turn around, though they never let go. As Anna finally took a look at the one behind her, she saw... Elsa. But not her Elsa. This one was wearing what looked like a Victorian military suit tailored for women, and her hair was in a low ponytail instead of the signature side braid that her older sister wore just moments ago before they were separated.

"Fuck," Anna whispered. When she saw Elsa raised an eyebrow, she shook her head, _no this was not the time to question her sexuality and morals_. "No, wait, what- Elsa?"

Elsa pulled her into a tight embrace, "I'm sorry, Anna, I'm so sorry. I know it was way out of line for me to pull that card. Can we go home now, please?"

Anna blinked. Her hands, tightly squeezed between their chests, reached out and returned the hug with a light squeeze. "Okay…?"

"You look… different, it's a good different," Anna stuttered, looking at Elsa's attire. "Why are you wearing it though? What happened to your lab coat?"

Elsa gave Anna a strange look, "What are you talking about? I've been wearing this, all day in fact. What about you? The last time I saw you, you were heading to your quarters to change. You didn't have these… weird clothes." Elsa looked at Anna's clothes, studying them. "In fact… what are these?" She pointed at Anna's legs. "Are you wearing men's clothes?"

For a moment, Anna couldn't speak-she was too stunned by the absurd words Elsa was saying. "Men's clothes?! Elsa, these are just jeans!"

"'Jeans'?" the blonde echoed, pronouncing the word carefully, as if she had never come across it before. Her brow furrowed, and her grip tightened ever so slightly on Anna. "Are you feeling all right? Do you need to see a doctor?"

But before Anna could answer, an explosion rocked the graveyard.

* * *

"A-Anna?"

"'Fraid not." A gruff voice answered as a large man stepped into view. His shaggy blonde hair looked like it hadn't seen a proper pair of scissors in years and he was covered head to toe in dirt. He gripped a shovel in his gloved hands. At his feet, a large, brown mutt panted up at her with shining eyes. Elsa recognized the two immediately.

"Kristoff!" She smiled at him, feeling relief. "Sven. Thank goodness! Look, I can't find Anna, have you seen her?"

But before she could start approaching him, the muscular blond man had done that first and landed a punch to her left cheek. Elsa was so shocked that she couldn't even register the pain for a moment after being sent backward for a few steps.

"What the hell was that for Kristoff?! Ow." She could taste the blood spilling out from her nipped tongue now and felt her anger raising.

"What was that for, huh? How about trying to elope with my fiancee? Now don't play games with me, where is MY Anna?!"

"The fu-" Right at that moment, she heard a scream. It continued into yet another louder and more desperate scream. It's Anna. There's no doubt about it, she could recognize her baby sister's voice no matter where. All anger for Kristoff disappeared, all confusion at his accusations be damned, the only thing on her mind right now was running towards the voice and making sure Anna is safe.

As they got closer, the screams got louder, and Elsa's heart raced faster. She could only wonder what had happened to her sister. The broken wooden excuse of a door slammed open, and Kristoff shoved her aside, rushing into the house. "Anna!"

Shots were fired.

And Elsa dared herself to take a step in. The wooden planks creaked and all eyes landed on her. Anna, _her_ Anna, without her goggles and lab coat but with soot on her clothes Anna, tears streaming down her face, was sitting in a couch all tied up.

A Gerda-look-alike rocked in her chair and laughed, "No heroes to save you now. Where's the money?"

Elsa swallowed past the panic climbing up her throat at such a dangerous situation. To think that their simple tinkering with time travel could lead to something like this…

"Anna, we'll get through this, okay?" she said shakily, and Gerda chuckled, as if amused by her hope.

"Th-There was another explosion, and...and I tried to get back to you," Anna nearly sobbed, not listening to Elsa's words at all, "And...And I saw Gerda, so I figured...I figured she'd help-"

The Gerda-look-alike laughed once more, as if to further prove how horrible of a mistake it had been.

"Elsa, I just want to go home…" Anna whimpered, her voice the smallest Elsa had ever heard from her, and something cold wrapped at the base of her spine as something turned to ash in her mouth.

 _This is all my fault. I never should've dragged her into this project. I never should've tried to...to impress her this way._

Her hands clenched at her sides...and as if on cue, an explosion rocked the house.

* * *

When Elsa's head stopped ringing from the force of the explosion, the first thing that registered was the sharp scent of chemicals that often fermented a laboratory and she was reminded of home. She let out a soft sigh and hoped that it was a sign that her and Anna would be home again soon if this was the case.

Elsa coughed out the smoke that caught in her lungs and heard another in front of her. She rubbed the dust out of her eyes and waited for the smoke to clear up. Silence filled wherever they were and she soon saw familiar grey tiles on the floor and blast marks surrounding her.

Her lips twitched eagerly and she felt as if she felt joy for the first time in forever. When the coughing stopped, Elsa slowly took a step forward, but there was no one in front of her when the fog cleared.

"Elsa?" Anna whispered.

"Anna?" A tear fell. She ran to the person, just sitting a few meters in front, in the corner of her room, leaning against the wall. She knelt down and grabbed her sister's hand to check, "Anna? Is that really you? Not some… some… I don't even know… Are you okay?"

There were red marks on her wrists and the dried up tears on her cheeks. Although she hated the sight of them, her heart hummed in relief.

 _It was Anna, alright._

Anna didn't bother answering the question. She leaned forward and crushed Elsa in a tight embrace and continued her soft sobbing. Elsa returned the hug just as fiercely and slightly rocked them both in a comforting rhythm. She didn't allow herself to tremble. Not when her baby sister was shaking in her arms.

"It's all okay now, Anna. You're okay." Elsa didn't know what to say except whispering sweet nothings into her sister's ears.

After a full ten minutes of just sitting on the floor and hugging, Anna began to calm down and stood up, yanking Elsa up with her and dragging her towards the exit.

"Wait wha-" But Elsa was cut off before she could finish. It seemed some higher power above decided she isn't allowed to finish any of her sentence today. This time though… it's by Anna's sudden turning around and crashing her lips on hers.

Perhaps both of them were caught up in the moment, or perhaps brushing so close to death sparked a greater awareness for what was dearest to them-whichever the case, they were finally together again, reunited through time.

They were finally home.

* * *

 **Epilogue**

It's been a week since that dangerous adventure. Elsa wouldn't want to change a thing though because it was what granted her the girl she wanted to have the most. She and Anna still hadn't talked about when and for how long they've harbored these feelings for each other, but they have all the time in the world for that. There was one thing she wanted to ask right now though…

"Anna, why the sudden interest in buying suits for me?"

She never got an answer for that, unfortunately. Every time she voiced the question, Anna just blushed and said vaguely that Elsa's wardrobe needed more variety. And when she pressed further, Anna just snapped at her. So the smart thing to do would be keeping her mouth shut and investigate later. Though she had a feeling it had something to do with their trip to the past.

 _ **FIN.**_

* * *

A/N: Participants this time are Squaresrcool, Wolfypuppy7, Elsanna-has-ruined-me, Liamgrbd, the-wandering-quill, Mad-Frozen, Nopantsparade. Thank you everyone.


End file.
